Pretty sure the indycar doesn't fit a standard chassis, I'm sure the chassis is longer.
This is taking me back ot when I used to race the Tamiya F1's in the BRCA series and winter series -Brca and Ashby multi formula.
Paint up many F1 replica shells like the Simtec, williams 91, mclaren hakinen, I also did a silk cut jaguar, purple and white scheme. Ad used to do a Pepsi' scheme to challenge Dez Chands 'Coke' scheme.

.....never beat it though! lol.
The black Sauber used to be the shell to race though. For some reason the wings were spot on for handling.
We used to use the diffuser to great effect, but it got banned.